如何断定是闰年？

按照奇猫老师的教程开始练习。
1.年份是能够被 400整除
2.年份能够被4整除，而且是而且不能被100整除。

按照教程的作法：
year=input('year:')
year=int(year)
if year % 400==0:
print('cast1: % d is leapyear' % year)
elif year% 4==0 and year % 100 != 0:
print('cast2: % d is leapyear' % year)
else:
print('cast3: % d is not leapyear' % year)

参考其余同窗的作法：
year1=input('year1:')
year1=int(year1)
if year1 %400 ==0 or (year1 % 100 ==0 and year1 % 100 !=0):
print (year1,'是闰年')
else:
print( year1,'不是闰年')